Modelling the growth and utilisation of kikuyu grass (Pennisetum clandestinum) under grazing. 1. Model definition and parameterisation.

This paper describes a Tropical Pasture Simulator. This is a simple mechanistic model representing the growth of vegetative tropical pastures under rotational or continuous grazing with responses to N fertiliser, temperature and irradiance that can be used as a tool to study management options for the development of sustainable grazing systems. The model was derived as an adaptation of the ‘Hurley pasture models’ which were originally designed to simulate the growth of ryegrass. The model incorporates the processes of light interception and photosynthesis, leaf area expansion; growth, ageing and senescence of plant tissues, recycling of substrates from senescing tissues, nitrogen uptake, mineralisation of soil organic N, N leaching and grazing. The paper discusses the main structure of the model, its components and the main adaptations required to simulate the growth of tropical pastures. The model was parameterised for kikuyu grass (Pennisetum clandestinum) growing in dairy systems in highland regions of Costa Rica. This paper also discusses the sensitivity of parameter values and the development of minimum parameter datasets for time and cost-eAective implementation of the model. # 2000 Elsevier Science Ltd. All rights reserved.

[1]  Anthony J. Parsons,et al.  A theoretical analysis of grass growth under grazing , 1985 .

[2]  J. B. Dent,et al.  Integrating simulation models to optimise nutrition and management for dairy farms: a methodology. pp. 322-326. In: Livestock Farming Systems: Research, Development, Socio-Economics and the Land Manager. Dent, J.B. et al (Eds.). , 1996 .

[3]  J. H. M. Thornley,et al.  A model of nitrogen flows in grassland , 1989 .

[4]  L. Humphreys,et al.  Nitrogen response and stocking rate of Pennisetum clandestinum pastures: I. Pasture nitrogen requirement and concentration, distribution of dry matter and botanical composition , 1974, The Journal of Agricultural Science.

[5]  I. R. Johnson,et al.  Vegetative crop growth model incorporating leaf area expansion and senescence, and applied to grass , 1983 .

[6]  J. B. Dent,et al.  The role of systems research in grazing management: applications to sustainable cattle production in Latin America , 1997 .

[7]  W. Parton,et al.  A multi-species model for rangeland plant communities , 1988 .

[8]  R. Colman,et al.  Seasonal variation in the potential herbage production and response to nitrogen by kikuyu grass (Pennisetum clandestinum) , 1978, The Journal of Agricultural Science.

[9]  R. J. Thomas,et al.  Decomposition of leaf litter from tropical forage grasses and legumes , 1993 .

[10]  B. D. Hahn,et al.  A model for the evaluation of different production strategies for animal production from rangeland in developing areas: An overview , 1991 .

[11]  Mario Herrero.  Modelling dairy grazing systems : an integrated approach , 1998 .

[12]  W. Parton,et al.  Analysis of factors controlling soil organic matter levels in Great Plains grasslands , 1987 .

[13]  D. L. Scarnecchia,et al.  Tropical Pasture Utilisation , 1991 .

[14]  T. Stobbs,et al.  Influence of Progressive Defoliation of a Grass Sward on the Eating Behaviour of Cattle , 1976 .

[15]  K. Giller,et al.  Carbon turnover (δ13C) and nitrogen mineralization potential of particulate light soil organic matter after rainforest clearing , 1996 .

[16]  D. Ivory,et al.  Effect of Temperature on Growth of Five Subtropical Grasses. I. Effect of Day and Night Temperature on Growth and Morphological Development , 1978 .

[17]  M. Demment,et al.  Graphical analysis of sward depletion by grazing , 1992 .

[18]  James R. Ehleringer,et al.  Quantum Yields for CO2 Uptake in C3 and C4 Plants: Dependence on Temperature, CO2, and O2 Concentration , 1977 .

[19]  Donald R. Zak,et al.  Nitrogen cycling in coffee agroecosystems: net N mineralization and nitrification in the presence and absence of shade trees , 1994 .

[20]  J. Thornley.  Mathematical models in agriculture : a quantitative approach to problems in agriculture and related sciences , 1985 .

[21]  R. Huggett.  Mathematical models in agriculture: France, J. and Thornley, J.H.M. London: Butterworths, 1984. 335 pp. £35 hardback , 1985 .

[22]  G. Stanhill.  Book reviewTerrestrial nitrogen cycles: F.E. Clark and T. Rosswall (Editors), Ecological Bulletins 33, NFR (Swedish National Research Council), Stockholm, 1981, 714 pp., US $56.00, ISBN 91-546-0290-4 , 1982 .

[23]  G. Murtagh.  Factors affecting the growth of kikuyu. II. Water supply , 1988 .

[24]  J. Hodgson.  The control of herbage intake in the grazing ruminant , 1985, Proceedings of the Nutrition Society.

[25]  D. Zak,et al.  Nitrogen loss from coffee agroecosystems in Costa Rica : leaching and denitrification in the presence and absence of shade trees , 1995 .

[26]  J. B. Dent,et al.  The Plant/Animal Interface in Models of Grazing Systems , 2018, Agricultural Systems modeting and Simulation.

[27]  J. B. Dent,et al.  Modelling the growth and utilisation of kikuyu grass (Pennisetum clandestinum) under grazing. 2. Model validation and analysis of management practices , 2000 .

[28]  I. R. Johnson,et al.  Plant and Crop Modelling: A Mathematical Approach to Plant and Crop Physiology , 1990 .

[29]  I. Gordon,et al.  Sources of variation in the foraging efficiency of grazing ruminants , 1996 .

[30]  H. W. Hunt,et al.  Phoenix, a model of the dynamics of carbon and nitrogen in grassland soils , 1981 .

[31]  K. Mccree,et al.  An equation for the rate of respiration of white clover grown under controlled conditions. , 1970 .

[32]  L. Humphreys,et al.  Nitrogen response and stocking rate of Pennisetum clandestinum pastures: II. Cattle growth , 1974, The Journal of Agricultural Science.

[33]  I. R. Johnson,et al.  A model of instantaneous and daily canopy photosynthesis , 1984 .

[34]  D. J. Minson,et al.  The feed intake and grazing behaviour of cattle grazing a crop of Lablab purpureus cv. Rongai , 1980, The Journal of Agricultural Science.

[35]  I. R. Johnson,et al.  Dynamic model of the response of a vegetative grass crop to light, temperature and nitrogen , 1985 .

[36]  J. Wilson.  Cell wall characteristics in relation to forage digestion by ruminants , 1994, The Journal of Agricultural Science.

[37]  M. Norman,et al.  Proceedings of the XI International Grassland Congress , 1972 .

[38]  A. Parsons,et al.  ANALYSIS OF THE COEXISTENCE MECHANISMS FOR GRASSES AND LEGUMES IN GRAZING SYSTEMS , 1996 .

[39]  D. Richter,et al.  ENVIRONMENTAL IMPACTS OF NITRIFICATION AND NITRATE ADSORPTION IN FERTILIZED ANDISOLS IN THE VALLE CENTRAL OF COSTA RICA , 1994 .

[40]  D. Minson,et al.  The voluntary intake, digestibility, and retention time by sheep of leaf and stem fractions of five grasses , 1973 .

[41]  E. Ungar,et al.  HERBAGE INTAKE IN RELATION TO AVAILABILITY AND SWARD STRUCTURE: GRAZING PROCESSES AND OPTIMAL FORAGING , 1988 .

[42]  Claus Buschmann.  Plants and Microclimate — A Quantitative Approach to Environmental Plant Physiology, 2nd edition, H.G. Jones. Cambridge University Press (1992), 428 pp., (ISBN 0-521-42524-7). Price: 19.95 Pounds. , 1993 .

[43]  T. Stobbs.  The effect of plant structure on the intake of tropical pastures. I. Variation in the bite size of grazing cattle , 1973 .

[44]  I. Gordon,et al.  The allometry of food intake in grazing ruminants , 1987 .

[45]  Paul Teng,et al.  Systems approaches for agricultural development , 1993, Systems Approaches for Sustainable Agricultural Development.

[46]  D. Romney,et al.  The relationship between the control of meal size and the control of daily intake in ruminants , 1994 .

[47]  M. Ludlow.  Photosynthesis and Dry Matter Production in C3 and C4 Pasture Plants, With Special Emphasis on Tropical C3 Legumes and C4 Grasses , 1985 .

[48]  M. M. LUDLOwt,et al.  PHOTOSYNTHESIS OF TROPICAL PASTURE PLANTS , 1971 .

[49]  K. Giller,et al.  Driven by Nature: Plant Litter Quality and Decomposition , 1996 .

[50]  P. Vitousek.  Terrestrial nitrogen cycles: Some unanswered questions , 1984 .

[51]  R. J. Thomas.  The role of the legume in the nitrogen cycle of productive and sustainable pastures , 1992 .

[52]  K. Giller,et al.  Driven by nature: a sense of arrival or departure? , 1997 .

[53]  M. Frere,et al.  Agrometeorological crop monitoring and forecasting , 1979 .

[54]  K. Giller,et al.  Regulating N mineralization from plant residues by manipulation of quality. , 1997 .

[55]  R. H. Armstrong,et al.  Grazing Behaviour and Herbage Intake in Cattle and Sheep Grazing Indigenous Hill Plant Communities , 1986 .

[56]  I. Johnson,et al.  Modelling Photosynthesis in Monocultures and Mixtures , 1989 .